Rotary speed sensors for rail vehicles such as a locomotive or a multiple unit are used to reliably and precisely determine the rotary speed of the wheels of an axle. This applies in particular to traction control, but also to wheel-slip protection. Rotary sensors are further used in registration, train control, door control, etc. Multiple rotary speed sensors may be found in various parts of the vehicle. In particular the rotary speed sensors used for traction control are used in extremely harsh operating conditions encountered by rail vehicles.
It has turned out that the principle of scanning a ferromagnetic measurement scale with a magnetic sensor is extremely robust and often does not fail even if a seal has failed and the pulse generator is covered with a layer of brake dust or other dirt.
Phonic wheels used as encoder devices of this type are usually machined from stainless steel with a DIN-867 teeth design and are, therefore, fairly expensive. Some cost-saving potentials have been achieved by integrating the phonic wheel with an end cap as used for clamping the inner ring of a railway bearing onto the axle, e.g., in the SKF Axletronic odometer for axle box front covers described under http://evolution.skf.com/zino.aspx?articleID=15221. A further bearing assembly with a metallic tooth ring is disclosed e.g., in U.S. Pat. No. 4,069,435.
The invention addresses the problems of simplifying the manufacture, maintenance and exchange of the encoder impulse wheel in a sensor arrangement, reducing the costs thereof and simplifying its adaptation to different sensor designs.